China is conducting military drills in the South China Sea in an area between its southern province of Hainan and Vietnam, media reports said on Saturday.
The Bangkok Post reported that Beijing has warned ships to stay away from the region.
The Hainan Maritime Safety Administration said the drills would last until March 15.
In a statement late on Friday, the Chinese administration provided coordinates for an area between Hainan's Sanya and the Vietnamese city of Hue.
Earlier, Vietnam had slammed China for infringements on its sovereignty for entering part of the area that is well within Vietnam's 200 nautical miles exclusive economic zone.
China claims a large part of the disputed waterway and has built artificial islands on some of its reefs and islets, to widespread concern from several countries including the United States.
Experts say that China's claims are inconsistent with the 1982 Law of the Sea Convention.
The United States has repeatedly called on China to conform its maritime claims to international law as reflected in the Law of the Sea Convention.
It has also called China to cease its unlawful and coercive activities in the South China Sea.
